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M Seul

Publications and source records attributed to M Seul.

16 recordsLinked to original sources
PubMed2004

Multiplexed analysis of polymorphisms in the HLA gene complex using bead array chips.

A novel custom bead array technology is introduced, and it is applied to multiplexed analysis of highly polymorphic human leukocyte antigen (HLA) genetic loci. Our technology combines the construction of probe libraries on color-encoded microparticles (beads) with semiconductor chip processing to produce custom-designed high-density bead array chips in large quantities. Using this novel assay format, two modes of parallel molecular typing of the HLA complex were implemented, namely direct hybridization, illustrated here for class II HLA-DR, and a novel format of on-chip polymerase-mediated primer elongation, illustrated here for class I HLA-A, HLA-B, and HLA-DR using patient and reference cell-line DNA samples. Hybridization-mediated multiplexed analysis of polymorphism method was validated with 142 samples, resulting in 100% concordance with sequence-specific oligonucleotide typing results and a concomitant average of 40% less allele ambiguity. In addition, elongation and hybridization reactions were combined to identify multiple polymorphisms on the same phase of DNA for allele identification.

HLA Antigens↗
PubMed1986

Lateral diffusion of specific antibodies bound to lipid monolayers on alkylated substrates.

We have measured the lateral mobility of fluoresceinated monoclonal IgG antibodies bound specifically to a spin label lipid hapten in phospholipid monolayers supported on alkylated silicon oxide surfaces. Dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine monolayers containing 5 mol% of the lipid hapten were transferred by conventional Langmuir-Blodgett techniques onto substrates alkylated with hydrocarbon chains containing 10, 16, and 18 carbon atoms. We show that the diffusion of the bound antibodies depends on their lateral density, the composition of the lipid monolayer, and the nature of lipid coupling to hydrocarbon chains on the alkylated substrate. Antibody diffusion coefficients at low antibody densities are within a factor of 2 of those displayed by the lipid hapten in the absence of the bound antibody. High antibody densities result in reduced antibody mobility, but the lateral diffusion of unbound lipids is unaffected.

Antibodies↗
PubMed1984

Superoxide enhances photobleaching during cellular immune attack against fluorescent lipid monolayer membranes.

Lipid hapten-containing monolayer membranes with bound, anti-hapten antibody molecules serve as model immunological target membranes. Targets with bound-IgG trigger guinea pig macrophages to (a) adhere, (b) spread, (c) release lysosomal enzymes, and (d) increase cyanide-insensitive oxygen consumption. When the target membranes are derivatized with fluorescein, there is a 2-3-fold enhancement in the rate of fluorescein photobleaching in regions of cell-monolayer contact. This effect is due to release of O2- from macrophages, as shown by inhibition with superoxide dismutase and by the fact that enhanced photobleaching is not observed with cells of the RAW264 macrophage line, which undergo responses (a)-(d), but do not release O2- extracellularly. The O2- dependent photobleaching reaction appears to be relatively specific for fluorescein, as it did not occur with two other fluorophores, 4-nitrobenz-2-oxa-1,3-diazole and tetramethyl-rhodamine. Because stimulated neutrophils release large quantities of O2-, the photobleaching of fluorescein-labeled target membranes in response to neutrophils was examined. Monolayer membranes with specifically bound IgG caused neutrophils to adhere and become markedly motile during incubation at 37 degrees C. Like macrophages, neutrophils induced O2- -dependent photobleaching of fluorescein-labeled IgG in regions of cell-monolayer contact. In addition, neutrophils gave rise to a slower, nonphotochemical loss of fluorescence in the same contact regions. The latter effect is apparently due to cleavage of target-bound fluorescent IgG by proteolytic enzymes secreted by the neutrophils in response to the target surface.

Animals↗
PubMed1983

X-ray diffraction by phospholipid monolayers on single-crystal silicon substrates.

Monolayers of dipalmitoyl phosphatidylcholine have been transferred from an air-water interface to single-crystal silicon wafers previously alkylated with octadecyltrichlorosilane. By using synchrotron radiation it has been found possible to observe diffraction by single-crystal regions of these monolayers with negligible background scattering from the solid substrate. In one series of experiments, diffraction signals at Bragg spacings of 0.4247 +/- 0.0002 nm and 0.4253 +/- 0.0002 nm were observed. The supported phospholipid monolayer crystals show remarkably high in-plane order: the positional coherence length is at least 500 nm and the orientational order is better than 0.01 degrees . Preliminary temperature scans were carried out. The data reveal the existence of a phase transition at about 65 degrees C.

Journal Article↗
PubMed1982

Theory of periodic structures in lipid bilayer membranes.

An approximate, new model for the structure of the periodic, undulated P(beta'), phase of phosphatidylcholine bilayers is proposed. The properties of this phase are deduced by minimizing a Landau-de Gennes expression for the bilayer free energy when this free energy contains a term favoring a spontaneous curvature of the membrane. The theoretical calculation leads to a model for the P(beta') phase of phosphatidylcholine bilayers having a number of novel physical properties, including periodic variations in membrane "fluidity."

Journal Article↗